Radiation multiplies Salmonella's anti-tumor properties

Traditional radiation therapy, when combined with a genetically modified form of the deadly bacterium Salmonella, could help some cancer patients, Yale scientists have found.

Writing in the European Journal of Cancer, the scientists say they have developed a nontoxic strain of the dangerous “wild type” of Salmonella and used it in conjunction with X-rays to fight tumors in mice. The study, done in collaboration with Vion Pharmaceuticals, showed a remarkable gain in the ability to halt, although not completely eliminate, tumor growth.

Initial results from a Phase I clinical trial indicated that the bacterium can safely be used in humans. Yale scientists John M. Pawelek, Ph.D., K. Brooks Low, Ph.D., and David G. Bermudes, Ph.D., who is also director of biology at Vion, have received a patent for the cancer vector.

Pawelek, a senior research scientist in the Department of Dermatology, said the team was surprised at the effectiveness of the two therapies together. While either radiation or Salmonella alone prevented cancer growth for as much as three weeks, the combination stopped the tumors for more than twice as long.

While treating cancer patients with forms of bacteria has been done for at least 100 years, the reasons for its occasional success have eluded scientists. New ways of altering Salmonella and combining it with radiation are the novel aspects of the current work. “You can go into great detail about why X-rays and Salmonella are so effective together, but that is really speculation at this point,” Pawelek said. “We have discovered a novel therapy, and one of the things we are doing now is trying to understand how it works.”